CLASSIFICATION OF DAHLIAS

DAHLIAS ARE AVAILABLE in a multitude of sizes, forms, and colors. In fact, one of the alluring characteristics of dahlias is the huge range of bloom sizes and types, from the tiny two-inch (or less) pompons to the huge sixteen-inch giants.

A detailed classification system is used by the American Dahlia Society to catalog the thousands of varieties that now exist – and the new ones developed each year. The American Dahlia Society annually publishes the Classification and Handbook of Dahlias, which lists thousands of dahlia varieties, the latest form definitions, and other valuable information.

FORM

Dahlias are classified partially by their shape or form. There are dahlias which are fully double with the central rays (petals) spirally displayed, such as the formal decorative, informal decorative semi-cactus, cactus, incurved cactus, laciniated, ball, miniature ball, pompon, waterlily, and stellar types.

Then there are dahlias which are referred to as open centered. Those include the peony, anemone, collarette, orchid, orchette, single, and mignon single.

There are also dahlias classified as novelty, which means they have a form that doesn’t fit any of the other classifications.

The mature petals which determine the size of the dahlia also determine the dahlia formation.

DOWNLOAD THE FULL LIST OF DAHLIA TYPES

Click the button below to access a full list of all the dahlia forms, and their descriptions, currently recognized by the American Dahlia Society.
By-the-book definitions are basically as described in the official dahlia literature; notes are included to help translate the jargon.
All this page’s information is also in the downloadable PDF below.

The latest form descriptions and lists of currently exhibited varieties are available in the Classification and Handbook of Dahlias. This reference guide is published yearly by the American Dahlia Society and can be purchased online at dahlia.org.

PETAL FORMATION

Dahlia form definitions often refer to petal formation. For instance, the definition for formal decorative dahlias indicated that the petals should be flat, partially revolute, or partially involute.

Unfortunately, it isn’t always apparent just what those definitions mean. To demystify this aspect of dahlia classification, here are definitions for four important petal characteristics accompanied by clarifying illustrations.

INVOLUTE

The edges of the petals roll forward along the edge. When fully involute the edges touch or overlap so only the reverse of the petal is visible. Ball, miniature ball, and pompon dahlias are some with involute petals. The bloom pictured is a miniature ball variety.

REVOLUTE

The edges of the dahlia petals roll backward along the edge. When fully revolute they roll so much the edges of the petals touch.

LACINIATED

The petals are split at the tips. There is a twisting in the area of the split giving an overall fringed effect. The best laciniated dahlias have significant splits at the tips of the petals, not just small notches.

COLLARETTE

The petals are actually compound. While a cursory examination of a collarette dahlia may lead one to believe there are 2 rows of petals, the opposite is true. The “collar” is an integral part of each petal.

SIZE

In addition to form, dahlias are also classified by size. Each dahlia size (determined by bloom diameter in inches) is given a letter code, such as AA for the largest ones, and MS (Mignon Single) for the smallest.

SIZE CLASSIFICATIONS

(in diameter)

AA (Giant) …………… over 10″
A (Large) …………….. over 8 and up to 10″
B (Medium) ………….. over 6 and up to 8″
BB (Small) …………… over 4 and up to 6″
M (Miniature) ………… up to 4″
BA (Ball) ……………… over 3½”
MB (Miniature Ball) …. over 2 and up to 3½”
P (Pompon) ………….. up to 2″
S (Single) …………….. over 2″
MS (Mignon Single) …. up to 2″

COLOR

For purposes of dahlia classification all colors, shades tints, tones, and combinations thereof, known to be found in cultivated forms of dahlias have been grouped into the fifteen color groups listed below.

Classification is determined by the predominant color or colors appearing on the face of the petals. Classification by color of open-centered dahlias is determined by the predominant color appearing on the face of the petals except for orchid and orchettes varieties which are classified by the color on the reverse of the petals.

The official color guide for dahlia classification is the American Dahlia Society (ADS) color chart, published in 2004. The color guide can be purchased online from the American Dahlia Society at dahlia.org.

Here are the 15 recognized color groups, their abbreviations, and (when needed), an explanation.

White (W)

Yellow (Y)

Orange (OR)

Pink (PK)

Dark Pink (DP)

Red (R)

Dark Red (DR)

Lavender (L)

Purple (PR)

Bronze (BR)

LIGHT BLEND (LB)
Blends of the lighter tints and tones of pink, yellow, lavender, and other pastels; also two-toned varieties of pastel tints and tones in which the central rays are of a different color than the marginal rays.

FLAME (FL)
Blends of the light and high brilliance shades of red and yellow.

DARK BLEND (DB)
Blends of low brilliance and any of the dark reds or purples with contrasting color or colors.

VARIEGATED (V)
Two or more distinct colors on the fact of the ray florets (petals), the variegating color arranged in dots, flecks, splashes, stripes, or narrow lines which contrast with the basic color.

BICOLOR (BI)
Two distinctly clear and sharply separated colors on the face of the ray florets.

USING THE CLASSIFICATION SYSTEM

Assume you were exploring an online catalog from a commercial grower. In it you find a dahlia cultivar named Jennie which is listed as a B LC LB W/L. You may be attracted to the flower because your favorite aunt is named Jennie. However, you would like to know what it looks like. Using the abbreviated information from the catalog you would determine that it is a B size dahlia (between 6 and 8 inches in diameter), has laciniated form (split petals giving a frilled effect), and the color is a light blend mixture of white and lavender. The classification system is fairly simple and very useful when going through dahlia catalogs.

LET’S EVALUATE THE CLASSIFICATION OF THE POPULAR DAHLIA “NARROWS TRICIA” (B SC Y).

  • B indicates the size: over 6 inches up to 8 inches in diameter
  • SC indicates the form: semi-cactus
  • Y indicates the color: yellow

Note: semi-cactus dahlias have revolute petals that fold back along their axis.

(All this page’s information is also in the Downloadable PDF. Scroll up to find the button to download it.)